Two‐sided material support

usdShade currently does not declare the spec(the schema) for two-sided material(assign different material to the front and the back to a facet) (as of 2024 Jul)

https://openusd.org/release/wp_usdshade.html

So TinyUSDZ adds a purpose(namespace) token 'back' to material binding to support two-sided material for a while.

For example...

rel material:binding = </frontMat>
rel material:binding:back = </backMat>

rel material:binding:preview = </frontMat>
rel material:binding:back:preview = </backMat>

This also applies to GeomSubset materialBinding.

uniform token subsetFamily:materialBind:familyType = "partition"

def GeomSubset "dbl_mat"
{
      uniform token elementType = "face"
      uniform token familyName = "materialBind"
      int[] indices = [0, 1, 5, ...]
      rel material:binding:preview = </frontMat>
      rel material:binding:back:preview = </backMat>
}

TODO

• Check if this definition can co-exist with Material binding collection